1. Field of the Invention
The present invention relates to a device and a method used in a wireless communication system, and more particularly, to a device and a method of handling an offload parameter according to a cell selection in a wireless communication system.
2. Description of the Prior Art
A long-term evolution (LTE) system supporting the 3rd Generation Partnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standard are developed by the 3GPP as a successor of the universal mobile telecommunication system (UMTS) for further enhancing performance of the UMTS to satisfy increasing needs of users. The LTE system includes a new radio interface and a new radio network architecture that provides high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes at least one evolved Node-B (eNB) for communicating with at least one user equipment (UE), and for communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control.
A LTE-advanced (LTE-A) system, as its name implies, is an evolution of the LTE system. The LTE-A system targets faster switching between power states, improves performance at the coverage edge of an eNB, increases peak data rate and throughput, and includes advanced techniques, such as carrier aggregation (CA), coordinated multipoint (CoMP) transmissions/reception, uplink (UL) multiple-input multiple-output (UL-MIMO), licensed-assisted access (LAA) using LTE, etc. For a UE and an eNB to communicate with each other in the LTE-A system, the UE and the eNB must support standards developed for the LTE-A system, such as the 3GPP Rel-10 standard or later versions.
Network operators propose to offload network traffic of the LTE/LTE-A system to a wireless local area network (WLAN) operated in an unlicensed band, to ease load of the network traffic. For example, the eNB may provide services to the UE via the WLAN. However, according to the 3GPP standard, it is not known how the UE handles one or more dedicated WLAN offload parameters after the UE performs a cell selection procedure. In one example, the UE may perform a cell selection procedure, after the UE transfers from a connected mode to an idle mode. The UE may not communicate with the eNB correctly, if the dedicated WLAN offload parameter(s) is not handled properly. Thus, how to handle the dedicated WLAN offload parameter(s) according to the cell selection procedure is an important problem to be solved.